1. Field of the Invention
The present invention relates to a method for making a semiconductor device in which a Group II-VI compound semiconductor layer is deposited onto a Group III-V compound semiconductor layer.
2. Description of the Related Art
High-density or high-resolution recording/reproducing has been required for optical recording disks and magnetooptical recording disks, and compound semiconductors emitting green or blue light have been intensively studied for achieving such a requirement.
Among them, a Group II-VI compound semiconductor having feasible prospects is composed of at least one Group II element, i.e., zinc, magnesium, manganese, beryllium, cadmium and mercury and at least one Group VI element, i.e., oxygen, sulfur, selenium and tellurium. Particularly, a ZnMgSSe mixed crystal is easily deposited on a GaAs mixed crystal substrate, and is suitable for the formation of guide layers and/or clad layers in the production of semiconductor devices, such as blue-light semiconductor laser devices (for example, refer to Electron. Lett., 28, p. 1798(1992); Electron. Lett., 29, p. 1488(1993); and Appl. Phys. Lett., 66, p. 656(1995)). Luminescent Group II-VI compound semiconductor devices have been produced by depositing a Group II-VI compound semiconductor layer onto a compound semiconductor substrate composed of Group III-V elements, such as GaAs, by molecular beam epitaxy.
A conventional luminescent Group II-VI semiconductor device, however, has many stacking faults which are originated near the interface between the Group III-V compound semiconductor layer and the Group II-VI compound semiconductor layer. The partial dislocation at the edge of the stacking fault region is degraded in the active layer by introducing a current flow, and that causes increased non-luminescent recombination centers in the active layer. The luminescent efficiency of the luminescent semiconductor device decreases with time, and thus the life of the device is restricted (refer to Guha et al., Appl. Phys. Lett., 63, p. 3107 (1993)). Consequently, the decrease in the stacking fault density in the Group II-VI compound semiconductor layer is essential for the achievement of an extended life of the device.
Although the reduction of the stacking fault density has been intensively studied in various institutes, the stacking fault density which has been reported is generally 5.times.10.sup.3 cm.sup.-2 or more at best, and no technology for consistently reducing the stacking fault density to 5.times.10.sup.3 cm.sup.-2 or less has been established (refer to L. H. Kuo et al., Appl. Phys. Lett., 69, p. 1408(1996); and Preprint of 43rd spring meeting, The Japan Society of Applied Physics and Related Societies, p. 27-ZD-1,2,3,4,5 spring in 1996).